Applicant's disclosure is directed generally towards a wireless communications network overlay for determining the location of mobile appliances.
The use of wireless communication devices such as telephones, pagers, personal digital assistants, laptop computers, etc., hereinafter referred to collectively as “mobile appliances”, has become prevalent in today's society. Recently, at the urging of public safety groups, there has been increased interest in technology which can determine the geographic position, or “geolocate” a mobile appliance in certain circumstances. For example, the Federal Communication Commission (FCC) has issued a geolocation mandate for providers of wireless telephone communication services that puts in place a schedule and an accuracy standard under which the providers of wireless communications must implement geolocation technology for wireless telephones when used to make a 911 emergency telephone call (FCC 94-102 E911).
In addition to E911 emergency related issues, wireless telecommunications providers are developing location-enabled services for their subscribers including roadside assistance, turn-by-turn driving directions, concierge services, location-specific billing rates and location-specific advertising.
To support FCC E911 rules to locate wireless 911 callers, as well as the location enabled services, the providers of wireless communication services are installing mobile appliance location capabilities into their networks. In operation, these network overlay location systems take measurements on RF transmissions from mobile appliances at base station locations surrounding the mobile appliance, and estimate the location of the mobile appliance with respect to the base stations. Because the geographic location of the base stations is known, the determination of the location of the mobile appliance with respect to the base station permits the geographic location of the mobile appliance to be determined. The RF measurements of the transmitted signal at the base stations can include the time of arrival, the angle of arrival, the signal power, or the unique/repeatable radio propagation path (radio fingerprinting) derivable features. In addition, the geolocation systems can also use collateral information, e.g., information other than that derived for the RF measurement to assist in the geolocation of the mobile appliance, i.e., location of roads, dead-reckoning, topography, map matching etc.
In a network-based geolocation system, the mobile appliance to be located is typically identified and radio channel assignments determined by (a) monitoring the control information transmitted on radio channel for telephone calls being placed by the mobile appliance or on a wireline interface to detect calls of interest, i.e., 911, (b) a location request provided by a non-mobile appliance source, i.e., an enhanced services provider. Once a mobile appliance to be located has been identified and radio channel assignments determined, the location determining system is first tasked to determine the geolocation of the mobile appliance and then directed to report the determined position to the requesting entity or enhanced services provider.
The monitoring of the RF transmissions from the mobile appliance or wireline interfaces to identify calls of interest is known as “tipping”, and generally involves recognizing a call of interest being made from a mobile appliance and collecting the call setup information. Once the mobile appliance is identified and the call setup information is collected, the location determining system can be tasked to geolocate the mobile appliance.
FIG. 1 shows a conventional mobile-appliance communication system having base stations 10a-c for communicating with a mobile appliance 20. Each base station 10 contains signal processing equipment and an antenna for transmitting to and receiving signals from the mobile appliance 20 as well as other base stations. A Base Station Controller (“BSC”) and/or Mobile Switching Center (“MSC”) 45 typically is connected to each base station 10 through wireline connection 41. A mobile appliance location determining sensor 30 i.e., wireless location sensor (“WLS”) may be positioned at some or all of the base stations 10 to determine the location of mobile appliance 20 within the signal coverage area of the communication system. A network overlay system is generally composed of two main components, one that resides at the base station that makes measurements on the RF signal emanating from the wireless device, the WLS 30, and one that resides at the mobile switch that tasks the WLS groups to collect data and then uses the data to compute a location estimate, this latter component is generally referred to as the Geolocation Control System (“GCS”) 50. In the normal course of operation, the GCS is tasked by an outside entity, e.g., the Mobile Positioning Center (“MPC”) 40, to generate a location estimate on a particular mobile appliance. The tasking is accompanied by information on the mobile of interest including the serving base station and sector for the call and the RF channel (frequency, time slot, CDMA code, etc.) being used by the wireless communications network to complete the wireless connection. Once the GCS receives this tasking, based on the serving sector, it tasks a set of WLS units to make measurement on the RF emission of the mobile. The WLS units make the measurements, and report them to the GCS. The GCS then computes a location estimate using some mathematical or data matching algorithm. Alternatively, control signaling on RF or wireline interfaces used to set up calls in the wireless network can be scanned to detect the placement of a call of interest. The signaling that occurs on the RF control channel can be used to determine location, or call setup/channel assignment parameters can be extracted from the control messaging to determine which traffic channel to use for location related measurements.
Network overlay location systems typically locate a mobile appliance on the traffic channels of a wireless network. The system typically uses sensors employing techniques of time difference of Arrival (“TDOA”) supplemented with Angle of Arrival (“AOA”) in some case to perform a multi-site location computation. The traffic channel assignment information is provided through a separate process, with one option being a wireline interface providing MOBINFO (IS-41 Mobile Information) parameters passed by the Mobile Positioning Center as part of the GPOSREQ (J-STD-036 Geolocation Position Request) message from the MPC to the GCS 50.
To meet the ever growing demand for mobile communication, wireless communication systems deploy repeater stations to expand range and concentration of coverage. In FIG. 1, a repeater 50a, associated with base station 10a, is located to extend the coverage area to encompass the back side of the mountain 1. The repeater 50b, associated with base station 10c, is mounted on a building and is used to provide service within the building 2.
Repeaters typically fall into two categories: (1) non-translating, also known as wideband, and (2) translating, also known as narrowband. As shown in FIG. 2a, non-translating repeater 250 simply passes the forward Ff1 and reverse Rf1 frequencies from the base station 210 and mobile appliance 220 respectively to and from the repeater coverage location. Often wideband repeaters are “in-building” or serve limited coverage areas. While the description of non-translating repeaters above and translating repeaters below are described in reference to frequency, their operation can equally be described in terms of channels, and the use of the term frequency should not be construed to limit the scope of the present disclosed subject matter.
A translating repeater assigns the mobile to a different traffic channel unbeknownst to the base station, mobile switch, MPC, and the base station controller. As shown in FIG. 2b, the translating repeater uses the base station traffic channel Rf1 for repeater 250 to base station 210 communication while the mobile appliance 220 utilizes a separate frequency Rf2 for mobile to repeater communications. Translating repeaters act similarly in the forward direction using Ff1 from the base station 210 to the repeater station 250 and Ff1 from the repeater station 250 to the mobile appliance 220. In both cases, the existence of the repeater is usually transparent to the network.
Repeaters typically communicate with the host base station via an RF link as shown in FIG. 3 between base station 310 and repeater 350a. This connection allows remote operation of the repeater without physical ties back to the host base station, which is particularly advantageous in rugged or other areas where laying lines are difficult or costly. Some repeaters, generally non-translating repeaters, use a fiber optic or copper wire “tether” instead of an RF link to communicate with the host base station as shown in FIG. 3, where base station 310 is connected to repeater station 350b by tether 351. RF signals are placed onto the tether at the repeater, and then summed into the normal base station antenna path at the antenna feed interface 311 at the host base station. After integration into the normal base station antenna path, the signal from the repeater is indistinguishable to the base station regarding its origin (e.g., from the base station antennas or from a tether). In this tether architecture as well, the host base station has no knowledge of the repeater's existence or that a call is being served by the repeater.
Neither the base station nor the switch knows that a repeater is serving a call. Therefore the GPOSREQ information from the MPC which, in part, originates from the switch, is not able to alert the Geolocation system that a repeater is in use. When a prior art network overlay location system attempts to locate a mobile being served by a repeater without knowing that a repeater is serving the mobile, a number of alternatives can occur. The location system may locate the mobile based on receiving only RF signals directly from the mobile at a sufficient number of sites to locate the mobile. This alternative is the same as if the repeater was not involved from the standpoint of the location system. Another alternative is that the location system would receive signals from the repeater backhaul link antenna, and produce a location. Thus, the location of the repeater antenna (rather than the mobile) would be the “worst case” geolocation computed location. For example, a repeater installed as an in-building distribution system would use indoor antennas to communicate with the indoor handsets, and an outdoor antenna to communicate with the host base station. If the geolocation system were unable to locate the mobile itself, the location of the outdoor antenna (the repeater) would be used. Since this is the location of the building housing the mobile, this is a much better location estimate than the Phase I cell-sector information and is often compliant within the FCC accuracy mandate over the given network. The Phase I system typically does not know of repeater existence and uses the host cell's cell-sector information for location. While acceptable in some cases, as identified above, using the location of repeater 50a in FIG. 1, would be of little use. In the case where the location system receives the RF signal from a mixed set of sources (some from the mobile and some from the repeater backhaul antenna), an erroneous location estimate can be generated. In the case where the location system does not receive RF at sufficient WLS sites to generate a location estimate due to the effects of the repeater action or transmitted power of the mobile or directionality of the repeated signal from the repeater backhaul antenna, no location estimates will be reported.
Therefore, there is a need in the prior art for a network overlay geolocation system and method of operation in a host wireless communication system that provides accurate geolocation of mobiles served by repeater stations. In order to accomplish this, there is a need to overcome the deficiencies in the prior art by employing a novel geolocation system and method that is capable of identifying when a mobile's signal is being received via a repeater.
In view of this need, it is an object of the disclosed subject matter to obviate the deficiencies in the prior art and present an improved method for determining the location of a mobile appliance in a wireless communication system with base stations and a repeater for communicating with the mobile appliance. The wireless communication system includes a mobile positioning center and the repeater is connected with a communication tether to the base station. A plurality of geolocation sensors are co-located with the plural base stations and the mobile positioning center provides mobile information to the geolocation system. The improvement includes the step of monitoring the communication system with the WLS and determining if a target mobile appliance is served by the at least one repeater.
It is also an object of the disclosed subject matter to present an improved method of determining the location of a mobile appliance in a wireless communication system having base stations and repeater stations for communicating with the mobile appliance. The repeater station is connected to the base stations with a communication tether. The improvement includes the steps of detecting signals from a target mobile appliance on the communication tether and using a known delay attributed to the communication tether and the respective repeater station to determine the location of the target mobile appliance.
It is another object of the disclosed subject matter to present an improved method for determining the location of a mobile appliance in a wireless communication system with base stations and repeater stations for communicating with the mobile appliance where a repeater station is connected to its base stations with a communication tether. The improvement includes determining the location of the repeater station using mobile information parameters received from an MPC and using the location of the repeater station, or the centroid of the repeater's coverage area, as the location of the mobile appliance.
It is still another object of the disclosed subject matter to present an improved method for determining the location of a mobile appliance in a wireless communication system with base stations and repeaters. The method includes the step wherein the repeater station relays a mobile appliance's signal on a different channel than the signal transmitted by the mobile appliance. The improvement includes relaying from the repeater station information regarding the channel of the mobile appliance's signal to a geolocation system and using the information to detect the mobile appliance's signal or repeater backhaul antenna signal and calculate the mobile appliance's location.
It is yet another object of the disclosed subject matter to present an improved method for determining the location of a mobile appliance in a wireless communication system with base station and repeaters, where the repeaters relay the mobile appliance's signal on the same channel as the channel in which the signal was received by the repeater, and where a mobile positioning center provides mobile information to assist in the location of the mobile appliance. The improvement includes using the first signal received from the mobile appliance at each of the plural base stations to determine the location of the mobile appliance.
It is an additional object of the disclosed subject matter to present a novel network overlay geolocation system for locating a mobile in a host wireless communication system. The host wireless communication system includes a base station and a repeater station connected by a communication tether. The network overlay geolocation system has a geolocation sensor attached to the communication tether between the base station and said repeater station.
It is also an additional object of the disclosed subject matter to present a novel wireless communication system for providing communication to and from a mobile appliance. The system includes a base station and a repeater station interconnected by a communication tether connected to the base station at an antenna feed interface and a mobile positioning center for providing mobile information. The network overlay geolocation system has a geolocation sensor co-located at the base station on the tether prior to the antenna feed interface.
These objects and other advantages of the disclosed subject matter will be readily apparent to one skilled in the art to which the disclosure pertains from a perusal or the claims, the appended drawings, and the following detailed description of the preferred embodiments.